Fix usage of isReady for usage collection of alerts and actions

[mikecote]

From #81944.

The following collectors need to change their isReady to properly wait for the task manager state to exist

Docs: src/plugins/usage_collection/README.md

isReady (added in v7.2.0 and v6.8.4) is a way for a usage collector to announce that some async process must finish first before it can return data in the fetch method (e.g. a client needs to ne initialized, or the task manager needs to run a task first). If any collector reports that it is not ready when we call its fetch method, we reset a flag to try again and, after a set amount of time, collect data from those collectors that are ready and skip any that are not. This means that if a collector returns true for isReady and it actually isn't ready to return data, there won't be telemetry data from that collector in that telemetry report (usually once per day). You should consider what it means if your collector doesn't return data in the first few documents when Kibana starts or, if we should wait for any other reason (e.g. the task manager needs to run your task first). If you need to tell telemetry collection to wait, you should implement this function with custom logic. If your fetch method can run without the need of any previous dependencies, then you can return true for isReady as shown in the example below.

[elasticmachine]

Pinging @elastic/kibana-alerting-services (Team:Alerting Services)